Bug 1509391 - [eslint] Ignore excluded files that mozlint wasn't able to handle automatically r=Standard8
Normally eslint handles its own file exclusions, but there are still some
globally excluded paths that |mach lint| passes in (e.g objdirs and things in
ThirdPartyPaths.txt).
This makes sure that if they show up in the 'config', we handle them.
Differential Revision: https://phabricator.services.mozilla.com/D12712